Hydraulic drive systems are known to help facilitate the conversion between mechanical energy (e.g., in the forming of rotating shafts) and hydraulic energy, typically in the form of pressure. One hydraulic drive system that is known for use with respect to vehicles is sometimes called a hydraulic launch assist. When a vehicle brakes, mechanical energy from the vehicle driveline is captured by the hydraulic drive system and stored in a high pressure storage device. When the vehicle accelerates, pressurized fluid in the high pressure storage device is released, converting the hydraulic energy into mechanical energy.
Unfortunately, there are various inefficiencies in using a hydraulic drive system. The efficiencies include issues related to a pump-motor that is inaccurately calibrated, changing temperatures affecting pressures within the hydraulic drive system, time required to place the hydraulic drive system into a normal operational state, the time for applying a clutch to facilitate the conversion between hydraulic energy and mechanical energy, and issues associated with changing states within the hydraulic drive system.